Automated Laser Power Control for Roughing and Finishing in Micro Laser Machining

摘要

Micro laser machining with ultra short pulsed Nd:YAG lasers enables micro structuring in nearly all kinds of solid materials regardless of their mechanical properties. Due to the high focusing possibility of laser beams smallest structures in the micro meter region can be realized with small heat affected zones. The drawback of the high miniaturization potential is the high machining time for machining of lager volumes. As a remedy new ablation strategies have been investigated. Roughing is used for ablation of high volumes with short ablation times while finishing is used for generation of the desired surface quality. High ablation rates for roughing can be achieved with high laser power densities in focal depth. It is influenced by the focal spot diameter and the laser power in focal depth which have to be controlled and adjusted in process. For the manipulation of the laser focal spot diameter an automated beam expander has been integrated into the laser beam path. Additional laser power control units (e.g. using acoustic emissions) allow the automated adjustment of laser power in focal depth for different focal diameters.